function base64() {}  

const _keyStr = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';

base64.encode = function (input) {
  let output = '';  
  let chr1, chr2, chr3, enc1, enc2, enc3, enc4;
  let i = 0;  
  input = this._utf8_encode(input);  
  while (i < input.length) {  
    chr1 = input.charCodeAt(i++);  
    chr2 = input.charCodeAt(i++);  
    chr3 = input.charCodeAt(i++);  
    enc1 = chr1 >> 2;  
    enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);  
    enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);  
    enc4 = chr3 & 63;  
    if (isNaN(chr2)) {  
      enc3 = enc4 = 64;  
    } else if (isNaN(chr3)) {  
      enc4 = 64;  
    }  
    output = output +  
      _keyStr.charAt(enc1) + _keyStr.charAt(enc2) +  
      _keyStr.charAt(enc3) + _keyStr.charAt(enc4);  
  }  
  return output;
}

base64.decode = function (input) {
  let output = '';  
  let chr1, chr2, chr3;  
  let enc1, enc2, enc3, enc4;  
  let i = 0;  
  input = input.replace(/[^A-Za-z0-9\+\/\=]/g, '');  
  while (i < input.length) {  
    enc1 = _keyStr.indexOf(input.charAt(i++));  
    enc2 = _keyStr.indexOf(input.charAt(i++));  
    enc3 = _keyStr.indexOf(input.charAt(i++));  
    enc4 = _keyStr.indexOf(input.charAt(i++));  
    chr1 = (enc1 << 2) | (enc2 >> 4);  
    chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);  
    chr3 = ((enc3 & 3) << 6) | enc4;  
    output = output + String.fromCharCode(chr1);  
    if (enc3 != 64) {  
        output = output + String.fromCharCode(chr2);  
    }  
    if (enc4 != 64) {  
        output = output + String.fromCharCode(chr3);  
    }  
  }  
  output = this._utf8_decode(output);  
  return output;      
}

base64._utf8_encode = function (string) {
  string = string.replace(/\r\n/g, "\n");  
  let utftext = '';  
  for (let n = 0; n < string.length; n++) {  
    let c = string.charCodeAt(n);  
    if (c < 128) {  
        utftext += String.fromCharCode(c);  
    } else if((c > 127) && (c < 2048)) {  
        utftext += String.fromCharCode((c >> 6) | 192);  
        utftext += String.fromCharCode((c & 63) | 128);  
    } else {  
        utftext += String.fromCharCode((c >> 12) | 224);  
        utftext += String.fromCharCode(((c >> 6) & 63) | 128);  
        utftext += String.fromCharCode((c & 63) | 128);  
    }  

  }  
  return utftext;      
}

base64._utf8_decode = function (utftext) {
  let string = "";  
  let i = 0;  
  let c = 0;
  let c1 = 0;
  let c2 = 0;  
  let c3 = 0;
  while ( i < utftext.length ) {  
    c = utftext.charCodeAt(i);  
    if (c < 128) {  
        string += String.fromCharCode(c);  
        i++;  
    } else if((c > 191) && (c < 224)) {  
        c2 = utftext.charCodeAt(i+1);  
        string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));  
        i += 2;  
    } else {  
        c2 = utftext.charCodeAt(i+1);  
        c3 = utftext.charCodeAt(i+2);  
        string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));  
        i += 3;  
    }  
  }  
  return string;      
}

module.exports = base64